1. Field of the Invention
The present invention relates to an ultrasonic sensor for use in an automotive vehicle, the ultrasonic sensor receiving ultrasonic waves reflected on an object to be detected.
2. Description of Related Art
Recently, an ultrasonic sensor has been mounted on an automotive vehicle to detect an obstacle located around the vehicle. Ultrasonic waves are transmitted from the vehicle, and the ultrasonic waves reflected on the obstacle are received by the ultrasonic sensor mounted on the vehicle. A distance of the obstacle from the vehicle and/or its two-dimensional or three-dimensional shape are detected based on the transmitted and received ultrasonic waves.
In this type of sensor, the position of the obstacle may be detected based on a time difference among plural sensors in receiving the reflected waves. The plural sensors are mounted on a receiving member that delivers the received ultrasonic waves to individual sensor elements. In this structure, however, there is a problem that a crosstalk of the ultrasonic waves occurs in the receiving member. That is, the received ultrasonic waves are not sufficiently separated to individual sensor elements, and accordingly, detection sensitivity of the ultrasonic sensor is lowered. To cope with this problem, JP-A-5-347797 proposes to fill a space between individual vibrating plates with an intercepting material for preventing transfer of the ultrasonic waves. In this manner, it intends to reduce an amount of crosstalk between neighboring vibrating plates.
However, the proposed structure of the ultrasonic sensor involves such a problem that a space for filling the intercepting material is required between neighboring vibrating plates. This makes the ultrasonic sensor large in size and adversely affects an ornamental design of the ultrasonic sensor that is mounted on a bumper of a vehicle.